Semiconductor device with reduced error operation caused by threshold voltage variation

ABSTRACT

An output circuit is driven by a first differential amplification circuit having an N-channel differential amplification stage that compares a reference voltage VREF with an input signal IN, and a second differential amplification circuit having a P-channel differential stage. An output of the first differential amplification circuit is given as the gate voltage of P-channel MOS transistors in the output circuit, and an output of the second differential amplification circuit is given as the gate voltage of N-channel MOS transistors in the output circuit. This realizes an input buffer with reduced error operations even under threshold voltage variations caused by process variations and others.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device, and moreparticularly to a semiconductor device including an input buffer thatreceives a signal from outside to transmit the signal to an internalcircuit.

2. Description of the Background Art

A semiconductor device includes an input buffer that receives a signalinput from outside. A conventional input buffer is constructed with adifferential amplification circuit of a current mirror load and aninverter.

FIG. 8 is a circuit diagram showing a construction of a conventionalinput buffer 200.

Referring to FIG. 8, the input buffer 200 includes a differentialamplification circuit 202 that is activated in accordance with a signalEN and compares a reference voltage VREF with an input signal IN, and aninverter 204 that receives and inverts an output of the differentialamplification circuit 202 and outputs an output signal OUT.

The differential amplification circuit 202 includes an N-channel MOStransistor 206 whose gate receives the signal EN and whose source isconnected to a ground node, and an N-channel MOS transistor 208 whosegate receives the reference voltage VREF and whose source is connectedto the drain of the N-channel MOS transistor 206.

The differential amplification circuit 202 further includes an N-channelMOS transistor 210 whose gate receives the input signal IN and whosesource is connected to the drain of the N-channel MOS transistor 206,and a P-channel MOS transistor 212 whose gate and drain are connected tothe drain of the N-channel MOS transistor 208 and whose source isconnected to a power supply voltage Vcc.

The differential amplification circuit 202 further includes a P-channelMOS transistor 214 whose gate is connected to the drain of the N-channelMOS transistor 208 and which is connected between the node to which thepower supply voltage Vcc is given and the drain of the N-channel MOStransistor 210, and a P-channel MOS transistor 216 whose gate receivesthe signal EN and which is connected between the power supply node andthe drain of the N-channel MOS transistor 210. An output signal A of thedifferential amplification circuit 202 is output from the drain of theN-channel MOS transistor 210.

The inverter 204 includes a P-channel MOS transistor 218 and anN-channel MOS transistor 220 both of which receive a signal A at thegates thereof and which are connected in series between the power supplynode and the ground node. An output signal OUT is output from theconnection node of the P-channel MOS transistor 218 and the N-channelMOS transistor 220.

When the signal EN is raised to a H-level, the N-channel MOS transistor206 is brought into a conducted state while the P-channel MOS transistor216 is brought into a non-conducted state. Then, the differentialamplification circuit 202 is activated and, if the input signal IN ishigher than the reference voltage VREF, the differential amplificationcircuit 202 outputs a L-level to the signal A, whereas if the inputsignal IN is lower than the reference voltage VREF, the differentialamplification circuit 202 outputs a H-level as the signal A.

However, regarding the amplitude of the output signal of thedifferential amplification circuit, it is not always the case that theH-level is the power supply voltage Vcc and the L-level is the groundvoltage. There are cases in which the H-level of the output signal islower than the power supply voltage Vcc or the L-level is higher thanthe ground voltage.

FIG. 9 is a waveform diagram for explaining an error operation of theinput buffer.

Referring to FIGS. 8 and 9, the input signal IN is repeatedly at ahigher voltage or at a lower voltage than the reference voltage VREFand, in accordance therewith, the output signal A of the differentialamplification circuit 202 alternately outputs the H-level and theL-level. However, since the L-level of the signal A is higher than athreshold voltage Vt of the inverter 204, the signal A does not crossover the threshold voltage of the inverter. Then, the output signal OUTof the inverter is fixed at the L-level.

Such a phenomenon occurs, for example, when the reference voltage VREFis low and, in such a case, it is difficult to raise the output of thedifferential amplification circuit above the threshold voltage of theinverter, thereby causing an error operation in which the output of theinverter remains invariable.

The threshold voltage of the inverter may change depending on productionvariations and, if the threshold value of the inverter changes, there isa problem of decrease in the production yield.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a semiconductor deviceincluding an input buffer that does not easily raise an error operationeven under threshold voltage variations of the inverter caused byproduction variations.

In summary, the present invention is directed to a semiconductor deviceincluding an input buffer circuit and an internal circuit.

The input buffer circuit receives a first input signal from outside. Theinput buffer circuit includes first and second differentialamplification circuits and an output circuit. The first differentialamplification circuit compares a voltage given by the input signal witha reference voltage and outputs complementary first and second outputsignals in which a high level of an output voltage is a power supplyvoltage and a low level is a first intermediate voltage between thepower supply voltage and a ground voltage. The second differentialamplification circuit compares the voltage given by the first inputsignal with the reference voltage and outputs complementary third andfourth output signals in which a low level of an output voltage is theground voltage and a high level is a second intermediate voltage betweenthe power supply voltage and the ground voltage. The output circuitoutputs complementary fifth and sixth output signals in accordance withthe first to fourth output signals.

The internal circuit operates in accordance with the fifth and sixthoutput signals.

Therefore, a principal advantage of the present invention lies in thatthe error operation in which the input signal is not transmitted to theinside can be prevented when the threshold voltage variations occur dueto process variations.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a schematic construction of asynchronous semiconductor storage device 1 which is an example of asemiconductor device;

FIG. 2 is a circuit diagram illustrating a construction of a clockbuffer 4 in FIG. 1;

FIG. 3 is an operation waveform diagram for explaining an operation ofthe clock buffer 4 shown in FIG. 2;

FIG. 4 is a circuit diagram illustrating a construction of a flip-flop 6a which is included in a control signal input buffer 6 in FIG. 1 andwhich receives a control signal from outside and takes it in with aninternal clock;

FIG. 5 is a circuit diagram illustrating a construction of an inside ofan input buffer 22 in FIG. 1;

FIG. 6 is a view for explaining a part of an address buffer 2 in FIG. 1;

FIG. 7 is a circuit diagram illustrating a construction of a predecodingcircuit 142 which is disposed near to a memory array and whichpredecodes an address;

FIG. 8 is a circuit diagram illustrating a construction of aconventional input buffer 200; and

FIG. 9 is a waveform diagram for explaining an error operation of theinput buffer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereafter, preferred embodiments of the present invention will bedescribed in detail with reference to the attached drawings. Here, likereference numerals in the drawings denote like or corresponding parts.

FIG. 1 is a block diagram illustrating a schematic construction of asynchronous semiconductor storage device 1 as an example of asemiconductor device.

Referring to FIG. 1, the synchronous semiconductor storage device 1includes memory array banks 14#0 to 14#3 each having a plurality ofmemory cells that are arranged in a matrix configuration; an addressbuffer 2 that takes in address signals A0 to A12 and bank addresssignals BA0 to BA1, which are given from the outside, in synchronizationwith clock signals CLKI, /CLKI and outputs an internal row address, aninternal column address, and an internal bank address; a clock buffer 4that receives a clock signal CLK and a clock enable signal CKE from theoutside and outputs clock signals CLKI, /CLKI, and CLKQ used in theinside; and a control signal input buffer 6 that takes in controlsignals /CS, /RAS, /CAS, /WE, and a mask signal DQMU/L, which are givenfrom the outside, in synchronization with the clock signals CLKI, /CLKI.

The synchronous semiconductor storage device 1 further includes acontrol circuit that receives an internal address signal from theaddress buffer 2 and receives control signals int.RAS, int.CAS, int.WEsynchronized with the clock signals from the control signal input buffer6 to output a control signal to each block in synchronization with theclock signals CLKI, /CLKI, and a mode register that holds the operationmode recognized in the control circuit. In FIG. 1, the control circuitand the mode register are represented by one block 8.

The control circuit includes a bank address decoder that decodesinternal bank address signals int.BA0, int.BA1, and a command decoderthat receives and decodes the control signals int.RAS, int.CAS, int.WE.

The synchronous semiconductor storage device 1 further includes rowdecoders that are disposed respectively in correspondence with thememory array banks 14#0 to 14#3 and decode a row address signal X givenfrom the address buffer 2, and word drivers for driving anaddress-designated row (word line) in the inside of the memory arraybanks 14#0 to 14#3 to a selected state in accordance with the outputsignals of these row decoders. In FIG. 1, the row decoders and the worddrivers are collectively represented by blocks 10#0 to 10#3.

The synchronous semiconductor storage device 1 further includes columndecoders 12#0 to 12#3 that decode an internal column address signal Ygiven from the address buffer 2 to generate a column selection signal,and sensing amplifiers 16#0 to 16#3 that sense and amplify data of thememory cells connected to the selected row of the memory array banks14#0 to 14#3.

The synchronous semiconductor storage device 1 further includes an inputbuffer 22 that receives a write data fiom the outside to generate aninternal write data, a write driver that amplifies the internal writedata from the input buffer 22 and transmits the internal write data tothe selected memory cell, a preamplifier that amplifies the data readout from the selected memory cell, and an output buffer 20 that performsa buffer processing on the data from the preamplifier and outputs thedata to the outside.

The preamplifier and the write driver are disposed respectively incorrespondence with the memory array banks 14#0 to 14#3. In FIG. 1, thepreamplifier and the write driver are represented by blocks 18#0 to 18#3as one block.

The input buffer 22 takes in the data signals DQ0 to DQ15 given from theoutside to the terminal in accordance with a strobe signal DS. Thisstrobe signal DS is a signal that constitutes a standard of the time foranother semiconductor device or the like, which outputs data to thesynchronous semiconductor storage device 1, to take in the data that areoutput in synchronization with the data. The synchronous semiconductorstorage device 1 receives the strobe signal DS, which is transmittedfrom the outside in parallel with the data and which is given to theterminal, as a standard for taking in the data signals.

The synchronous semiconductor storage device 1 further includes a Vrefgenerating circuit 24 that generates a reference voltage Vre. Thereference voltage Vref is input to the input buffer and constitutes astandard for a threshold value in taking in the data.

When the synchronous semiconductor storage device 1 outputs data to theoutside, the output buffer 20 outputs the data signals DQ0 to DQ15 insynchronization with the clock signal CLKQ, and outputs to the outsidethe strobe signal DS for another semiconductor device to take in thedata signals.

In such a synchronous semiconductor storage device 1, the clock signalCLK given from the outside is given by being converted by the clockbuffer 4 into the clock signals CLKI, /CLKI and CLKQ that are used inthe inside. For example, the clock signal CLKQ is given to the inputbuffer 22 and the output buffer 20; however, the clock delay time tillthe clock signal CLKQ is transmitted to the input buffer 22 ispreferably equal to the clock delay time till the clock signal CLKQ istransmitted to the output buffer 20.

FIG. 2 is a circuit diagram illustrating a construction of the clockbuffer 4 in FIG. 1.

Referring to FIG. 2, the clock buffer 4 includes a differentialamplification circuit 32 that receives a reference voltage VREF and aninput signal IN and outputs a differential output to a node NA and anode NC; P-channel MOS transistors 38, 36 for fixing the voltages of thenode NA and the node NC to the power supply voltage Vcc in accordancewith a signal EN; a differential amplification circuit 34 that receivesthe reference voltage VREF and the input signal IN and outputs adifferential output to a node NB and a node ND; N-channel MOStransistors 42, 40 for fixing the voltages of the nodes NB, ND to theground voltage in accordance with a signal/EN; and an output circuit 44that outputs output signals OUT, /OUT in accordance with the voltages ofthe nodes NA, NB, NC, ND.

The differential amplification circuit 32 includes an N-channel MOStransistor 50 whose gate receives the signal EN and whose source isconnected to the ground node, an N-channel MOS transistor 46 whose gatereceives the reference voltage VREF and which is connected between thenode NC and the drain of the N-channel MOS transistor 50, and anN-channel MOS transistor 48 whose gate receives the input signal IN andwhich is connected between the node NA and the drain of the N-channelMOS transistor 50.

The differential amplification circuit 32 further includes a P-channelMOS transistor 52 whose gate is connected to the node NC and which isconnected between the power supply node and the node NC, a P-channel MOStransistor 54 whose gate is connected to the node NA and which isconnected between the power supply node and the node NC, a P-channel MOStransistor 56 whose gate is connected to the node NC and which isconnected between the power supply node and the node NA, and a P-channelMOS transistor 58 whose gate is connected to the node NA and which isconnected between the power supply node and the node NA.

The P-channel MOS transistor 52 and the P-channel MOS transistor 56 forma first current mirror, and the P-channel MOS transistor 58 and theP-channel MOS transistor 54 form a second current mirror. In otherwords, the differential amplification circuit 32 uses a current mirrorof cross-coupling type as a load of differential amplification.

The differential amplification circuit 34 includes a P-channel MOStransistor 62 whose source is connected to the power supply node andwhose gate receives the signal /EN, a P-channel MOS transistor 64 whosegate receives the reference voltage VREF and which is connected betweenthe drain of the P-channel MOS transistor 62 and the node ND, aP-channel MOS transistor 66 whose gate receives the input signal IN andwhich is connected between the drain of the P-channel MOS transistor 62and the node NB, an N-channel MOS transistor 68 whose gate and drain areconnected to the node ND and whose source is connected to the groundnode, an N-channel MOS transistor 70 whose gate is connected to the nodeNB and which is connected between the node ND and the ground node, anN-channel MOS transistor 72 whose gate is connected to the node ND andwhich is connected between the node NB and the ground node, and anN-channel MOS transistor 74 whose gate is connected to the node NB andwhich is connected between the node NB and the ground node.

The output circuit 44 includes a P-channel MOS transistor 76 and anN-channel MOS transistor 78 which are connected in series between thepower supply node and the ground node and whose gates are respectivelyconnected to the nodes NA, NB, and a P-channel MOS transistor 80 and anN-channel MOS transistor 82 which are connected in series between thepower supply node and the ground node and whose gates are respectivelyconnected to the nodes NC, ND. A signal OUT is output from theconnection node of the P-channel MOS transistor 76 and the N-channel MOStransistor 78, and a signal /OUT is output from the connection node ofthe P-channel MOS transistor 80 and the N-channel MOS transistor 82.

FIG. 3 is an operation waveform diagram for explaining the operation ofthe clock buffer 4 shown in FIG. 2.

When the voltage of the input signal IN becomes higher than thereference voltage VREF at the time t1, the voltages of the node NA andthe node NB come to an L-level. At this time, with respect to the outputof the differential amplification circuit 32 of a differential typedriven by N-channel MOS transistors, the output amplitude is biased tothe vicinity of the power supply voltage Vcc, as shown by the voltage ofthe node NA.

On the other hand, with respect to the differential amplificationcircuit 34 of a differential type driven by P-channel MOS transistors,the output amplitude is biased to the vicinity of the ground voltage, asshown by the voltage of the node NB. Therefore, since the voltage of thenode NB is at the ground voltage at the time t1 to t2, the N-channel MOStransistor 78 of the output stage can be cut off by inputting thisvoltage to the N-channel MOS transistor 78.

Subsequently, when the voltage of the input signal IN becomes lower thanthe reference voltage VREF at the time t2, the voltages of the nodes NA,NB come to a H-level in accordance therewith. In this case, since thevoltage of the node NA is equal to the power supply voltage Vcc, theP-channel MOS transistor 76 can be cut off by giving this voltage to thegate of the P-channel MOS transistor 76. Therefore, the input signal canbe correctly transmitted to the output signal OUT.

Further, since the differential amplification circuits 32, 34 haverespective complementary output signals, a complementary output signal/OUT can be created by giving a signal to the gates of the P-channel MOStransistor 80 and the N-channel MOS transistor 82. With the use of aclock buffer circuit having a construction described above, the outputsignals OUT, /OUT can be correctly output even if the threshold value ofthe inverter is varied due to production variations, so that the clocksignals CLKI, /CLKI can be correctly generated.

Here, in this embodiment, an example is shown in which the input buffercircuit shown in FIG. 2 is used as a clock buffer; however, the usage isnot limited to clock buffers alone, and it can be used as another inputbuffer that receives an input signal from outside.

Next, explanation will be given on an advantage of the case in which abuffer circuit having such complementary outputs is used.

FIG. 4 is a circuit diagram illustrating a construction of a flip-flop 6a which is included in the control signal input buffer 6 in FIG. 1 andwhich receives a control signal from outside and takes it in with aninternal clock.

Referring to FIG. 4, the flip-flop 6 a includes an inverter 92 thatreceives and inverts an input signal A, an N-channel MOS transistor 94that transmits an output of the inverter 92 when the clock signal CLKIis at a H-level, an inverter 96 that inverts the output of the inverter92 transmitted by the N-channel MOS transistor 94, an inverter 98 thatfeeds an output of the inverter 96 back to an input part of the inverter96, an inverter 100 that receives and inverts the output of the inverter96, an N-channel MOS transistor 102 that is conducted in accordance witha clock signal /CLKI and transmits an output of the inverter 100, aninverter 104 that receives and inverts the output of the inverter 100transmitted by the N-channel MOS transistor 102 and outputs a signal B,and an inverter 106 that feeds an output of the inverter 104 back to aninput of the inverter 104.

By supplying complementary clocks with the use of a clock buffer such asshown in FIG. 2, the flip-flop 6 a need not incorporate a phase splitterthat generates complementary internal clocks from the clock signal. Inother words, in many cases, a flip-flop usually incorporates a phasesplitter such as an inverter that inverts the clock signal. Therefore,by omitting the inverter, the circuit construction can be simplified.

FIG. 5 is a circuit diagram illustrating a construction of an inside ofthe input buffer 22 shown in FIG. 1.

Referring to FIG. 5, the input buffer 22 includes an input buffercircuit 112 that receives the data strobe signal DS and outputs thesignals IDS, /IDS, and a latch circuit 114 that takes in the data signalDQ in accordance with the signals IDS, /IDS and outputs an even datasignal DATAE and an odd data signal DATAO.

The input buffer circuit 112 has a construction similar to that of theclock buffer 4 shown in FIG. 2, so that an explanation thereof will notbe repeated.

The latch circuit 114 includes an N-channel MOS transistor 116 that isconducted in accordance with the signal /IDS and transmits the datasignal DQ, an inverter 118 that receives and inverts the signaltransmitted by the N-channel MOS transistor 116 and outputs the evendata signal DATAE, and an inverter 120 that receives the output of theinverter 118 and feeds the output to an input of the inverter 118.

The latch circuit 114 further includes an N-channel MOS transistor 122that transmits the data signal DQ in accordance with the signal IDS, aninverter 124 that receives and inverts the data signal DQ transmitted bythe N-channel MOS transistor 122 and outputs the odd data signal DATAO,and an inverter 126 that receives the output of the inverter 124 andfeeds the output to an input of the inverter 124.

By adopting such a construction, complementary latch signals aresupplied to the latch circuit 114, thereby eliminating the need forincorporating a phase splitter in the inside. This can simplify thecircuit construction.

FIG. 6 is a view for explaining a part of the address buffer 2 shown inFIG. 1.

Referring to FIG. 6, the address buffer 2 includes an input buffercircuit 132 that receives address signals A0 to A2 and outputscomplementary signals AD0 to AD2, /AD0 to /AD2. Here, the input buffercircuit 132 includes an input buffer having a construction similar tothat of the clock buffer 4 shown in FIG. 2 and corresponding to each ofthe address signals A0 to A2, so that an explanation thereof will not berepeated.

FIG. 7 is a circuit diagram illustrating a construction of a predecodingcircuit 142 which is disposed near to the memory array and whichpredecodes an address.

Referring to FIG. 7, the predecoding circuit 142 includes a NAND circuit144 that receives signals /AD0, /AD1, /AD2, an N-channel MOS transistor146 that is conducted in accordance with the clock signal CLKI andtransmits an output of the NAND circuit 144, an inverter 148 thatreceives and inverts the output of the NAND circuit 144 transmitted bythe N-channel MOS transistor 146 and outputs a predecoded signal AX0,and an inverter 150 that receives and inverts an output of the inverter148 and feeds the output to an input of the inverter 148.

The predecoding circuit 142 further includes a NAND circuit 154 thatreceives signals AD0, /AD1, /AD2, an N-channel MOS transistor 156 thatis conducted in accordance with the clock signal CLKI and transmits anoutput of the NAND circuit 154, an inverter 158 that receives andinverts the output of the NAND circuit 154 transmitted by the N-channelMOS transistor 156 and outputs a predecoded signal AX1, and an inverter160 that receives and inverts an output of the inverter 158 and feedsthe output to an input of the inverter 158.

The predecoding circuit 142 further includes a NAND circuit 164 thatreceives signals AD0, AD1, AD2, an N-channel MOS transistor 166 that isconducted in accordance with the clock signal CLKI and transmits anoutput of the NAND circuit 164, an inverter 168 that receives andinverts the output of the NAND circuit 164 transmitted by the N-channelMOS transistor 166 and outputs a predecoded signal AX7, and an inverter170 that receives and inverts an output of the inverter 168 and feedsthe output to an input of the inverter 168.

Here, although not illustrated, the predecoding circuit 142 furtherincludes circuits that output predecoded signals AX2 to AX6 inaccordance with the output of the input buffer circuit 132.

As described above, by inputting an address signal with the use of aconstruction such as shown in FIGS. 6 and 7, the address can bepredecoded at a high speed before it is latched with the clock signal,thereby raising a speed of the address signal processing.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the spiritand scope of the present invention being limited only by the terms ofthe appended claims.

What is claimed is:
 1. A semiconductor device comprising: an inputbuffer circuit that receives a first input signal, said input buffercircuit including: a first differential amplification circuit comparinga voltage given by said first input signal with a reference voltage andoutputting complementary first and second output signals in which a highlevel of an output voltage is a power supply voltage and a low level isa first intermediate voltage between said power supply voltage and aground voltage, a second differential amplification circuit comparingthe voltage given by said first input signal with said reference voltageand outputting complementary third and fourth output signals in which alow level of an output voltage is said ground voltage and a high levelis a second intermediate voltage between said power supply voltage andsaid ground voltage, an output circuit outputting complementary fifthand sixth output signals in accordance with said first to fourth outputsignals; and an internal circuit operating in accordance with said fifthand sixth output signals.
 2. The semiconductor device according to claim1, wherein said output circuit includes: a first P-channel MOStransistor and a first N-channel MOS transistor respectively receivingat their gates said first and third output signals and connected inseries between a power supply node to which said power supply voltage isgiven and a ground node to which said ground voltage is given; and asecond P-channel MOS transistor and a second N-channel MOS transistorrespectively receiving at their gates said second and fourth outputsignals and connected in series between said power supply node and saidground node.
 3. The semiconductor device according to claim 2, whereinsaid first input signal is a clock signal, and said internal circuitincludes a first latch circuit that takes in a second input signal inaccordance with said fifth output signal, and a second latch circuitthat takes in an output of said first latch circuit in accordance withsaid sixth output signal.
 4. The semiconductor device according to claim2, wherein said input buffer circuit receives a data strobe signal assaid first input signal, said internal circuit includes a data inputbuffer circuit that takes in data signal from outside in accordance withsaid data strobe signal, and said data input buffer circuit includes: afirst and second gate circuits that transmit said data signal inaccordance with said fifth and sixth output signals respectively; andfirst and second latch circuits that respectively hold transmitted datasignals by said first and second gate circuits, said semiconductordevice further including a memory array that receives and stores saiddata signals held by said first and second latch circuits.
 5. Thesemiconductor device according to claim 2, wherein said input buffercircuit receives an address signal as said first input signal, saidinternal circuit includes a predecoding circuit that predecodes saidaddress signal, and said predecoding circuit includes: a plurality ofNAND circuits each of which receives either one of said fifth and sixthoutput signals; a plurality of gate circuits that respectively transmitoutputs of said plurality of NAND circuits in accordance with a clocksignal; and a plurality of latch circuits that hold the outputs of saidplurality of NAND circuits respectively transmitted by said plurality ofgate circuits, said semiconductor device further including a memoryarray for reading out data by specifying a position of a memory cell inaccordance with outputs of said plurality of latch circuits.
 6. Thesemiconductor device according to claim 2, wherein said firstdifferential amplification circuit includes: a first N-channel MOStransistor having its source connected to said ground node, a secondN-channel MOS transistor having its gate receiving said first inputsignal and connected between a drain of said first N-channel MOStransistor and a first internal node to which said first output signalis output, a third N-channel MOS transistor having its gate receivingsaid reference voltage and connected between the drain of said firstN-channel MOS transistor and a second internal node to which said secondoutput signal is output, a first P-channel MOS transistor having itsgate connected to said second internal node and connected between saidfirst internal node and said power supply node, and a second P-channelMOS transistor having its drain and gate connected to said secondinternal node and source connected to said power supply node; and saidsecond differential amplification circuit includes: a third P-channelMOS transistor having its source connected to said power supply node, afourth P-channel MOS transistor having its gate receiving said firstinput signal and connected between a drain of said third P-channel MOStransistor and a third internal node to which said third output signalis output, a fifth P-channel MOS transistor having its gate receivingsaid reference voltage and connected between the drain of said thirdP-channel MOS transistor and a fourth internal node to which said fourthoutput signal is output, a fourth N-channel MOS transistor having itsgate connected to said fourth internal node and connected between saidthird internal node and said ground node, and a fifth N-channel MOStransistor having its drain and gate connected to said fourth internalnode and source connected to said ground node.
 7. The semiconductordevice according to claim 6, wherein said first differentialamplification circuit further includes: a sixth P-channel MOS transistorhaving its gate and drain connected to said first internal node andsource connected to said power supply node, and a seventh P-channel MOStransistor having its gate connected to said first internal node andconnected between said second internal node and said power supply node;and said second differential amplification circuit further includes: asixth N-channel MOS transistor having its gate and drain connected tosaid third internal node and source connected to said ground node, and aseventh N-channel MOS transistor having its gate connected to said thirdinternal node and connected between said fourth internal node and saidground node.